IMO shorts as casual wear are only appropriate on extremely hot days, i.e. 100+ degrees F. Functionally speaking, shorts are designed for cooler wear and ease of movement. So, shorts that hang at or below your knees make little practical sense. It baffles me that modern basketball players wear such long shorts. I bet there would be many fewer turnovers if they reverted to the older style shorts. But that is another issue all together. Your average American man wears long shorts primarily for two reasons, they're the most readily available in stores and/or they have body issues. If you choose to wear shorts, you'll look more proportional if you wear them above the knee. How far above the knee you want to go depends on your personal preference and what activity you plan to engage in. For casual shorts, I prefer shorts that come to the lower mid thigh. (4"- 6" inseam). For swimming or some other athletic activity , I prefer a shorter inseam for greater range of motion (i.e. 3"- 4" inseam).